text: //===- ELF.h - ELF object file implementation -------------------*- C++ -*-===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file declares the ELFFile template class.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_OBJECT_ELF_H
  #define LLVM_OBJECT_ELF_H
  
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/BinaryFormat/ELF.h"
  #include "llvm/Object/ELFTypes.h"
  #include "llvm/Object/Error.h"
  #include "llvm/Support/Endian.h"
  #include "llvm/Support/Error.h"
  #include <cassert>
  #include <cstddef>
  #include <cstdint>
  #include <limits>
  #include <utility>
  
  namespace llvm {
  namespace object {
  
  StringRef getELFRelocationTypeName(uint32_t Machine, uint32_t Type);
  uint32_t getELFRelativeRelocationType(uint32_t Machine);
  StringRef getELFSectionTypeName(uint32_t Machine, uint32_t Type);
  
  // Subclasses of ELFFile may need this for template instantiation
  inline std::pair<unsigned char, unsigned char>
  getElfArchType(StringRef Object) {
    if (Object.size() < ELF::EI_NIDENT)
      return std::make_pair((uint8_t)ELF::ELFCLASSNONE,
                            (uint8_t)ELF::ELFDATANONE);
    return std::make_pair((uint8_t)Object[ELF::EI_CLASS],
                          (uint8_t)Object[ELF::EI_DATA]);
  }
  
  static inline Error createError(const Twine &Err) {
    return make_error<StringError>(Err, object_error::parse_failed);
  }
  
  enum PPCInstrMasks : uint64_t {
    PADDI_R12_NO_DISP = 0x0610000039800000,
    PLD_R12_NO_DISP = 0x04100000E5800000,
    MTCTR_R12 = 0x7D8903A6,
    BCTR = 0x4E800420,
  };
  
  template <class ELFT> class ELFFile;
  
  template <class ELFT>
  std::string getSecIndexForError(const ELFFile<ELFT> *Obj,
                                  const typename ELFT::Shdr *Sec) {
    auto TableOrErr = Obj->sections();
    if (TableOrErr)
      return "[index " + std::to_string(Sec - &TableOrErr->front()) + "]";
    // To make this helper be more convenient for error reporting purposes we
    // drop the error. But really it should never be triggered. Before this point,
    // our code should have called 'sections()' and reported a proper error on
    // failure.
    llvm::consumeError(TableOrErr.takeError());
    return "[unknown index]";
  }
  
  template <class ELFT>
  std::string getPhdrIndexForError(const ELFFile<ELFT> *Obj,
                                   const typename ELFT::Phdr *Phdr) {
    auto Headers = Obj->program_headers();
    if (Headers)
      return ("[index " + Twine(Phdr - &Headers->front()) + "]").str();
    // See comment in the getSecIndexForError() above.
    llvm::consumeError(Headers.takeError());
    return "[unknown index]";
  }
  
  static inline Error defaultWarningHandler(const Twine &Msg) {
    return createError(Msg);
  }
  
  template <class ELFT>
  class ELFFile {
  public:
    LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
    using uintX_t = typename ELFT::uint;
    using Elf_Ehdr = typename ELFT::Ehdr;
    using Elf_Shdr = typename ELFT::Shdr;
    using Elf_Sym = typename ELFT::Sym;
    using Elf_Dyn = typename ELFT::Dyn;
    using Elf_Phdr = typename ELFT::Phdr;
    using Elf_Rel = typename ELFT::Rel;
    using Elf_Rela = typename ELFT::Rela;
    using Elf_Relr = typename ELFT::Relr;
    using Elf_Verdef = typename ELFT::Verdef;
    using Elf_Verdaux = typename ELFT::Verdaux;
    using Elf_Verneed = typename ELFT::Verneed;
    using Elf_Vernaux = typename ELFT::Vernaux;
    using Elf_Versym = typename ELFT::Versym;
    using Elf_Hash = typename ELFT::Hash;
    using Elf_GnuHash = typename ELFT::GnuHash;
    using Elf_Nhdr = typename ELFT::Nhdr;
    using Elf_Note = typename ELFT::Note;
    using Elf_Note_Iterator = typename ELFT::NoteIterator;
    using Elf_Dyn_Range = typename ELFT::DynRange;
    using Elf_Shdr_Range = typename ELFT::ShdrRange;
    using Elf_Sym_Range = typename ELFT::SymRange;
    using Elf_Rel_Range = typename ELFT::RelRange;
    using Elf_Rela_Range = typename ELFT::RelaRange;
    using Elf_Relr_Range = typename ELFT::RelrRange;
    using Elf_Phdr_Range = typename ELFT::PhdrRange;
  
    // This is a callback that can be passed to a number of functions.
    // It can be used to ignore non-critical errors (warnings), which is
    // useful for dumpers, like llvm-readobj.
    // It accepts a warning message string and returns a success
    // when the warning should be ignored or an error otherwise.
    using WarningHandler = llvm::function_ref<Error(const Twine &Msg)>;
  
    const uint8_t *base() const { return Buf.bytes_begin(); }
  
    size_t getBufSize() const { return Buf.size(); }
  
  private:
    StringRef Buf;
  
    ELFFile(StringRef Object);
  
  public:
    const Elf_Ehdr *getHeader() const {
      return reinterpret_cast<const Elf_Ehdr *>(base());
    }
  
    template <typename T>
    Expected<const T *> getEntry(uint32_t Section, uint32_t Entry) const;
    template <typename T>
    Expected<const T *> getEntry(const Elf_Shdr *Section, uint32_t Entry) const;
  
    Expected<StringRef>
    getStringTable(const Elf_Shdr *Section,
                   WarningHandler WarnHandler = &defaultWarningHandler) const;
    Expected<StringRef> getStringTableForSymtab(const Elf_Shdr &Section) const;
    Expected<StringRef> getStringTableForSymtab(const Elf_Shdr &Section,
                                                Elf_Shdr_Range Sections) const;
  
    Expected<ArrayRef<Elf_Word>> getSHNDXTable(const Elf_Shdr &Section) const;
    Expected<ArrayRef<Elf_Word>> getSHNDXTable(const Elf_Shdr &Section,
                                               Elf_Shdr_Range Sections) const;
  
    StringRef getRelocationTypeName(uint32_t Type) const;
    void getRelocationTypeName(uint32_t Type,
                               SmallVectorImpl<char> &Result) const;
    uint32_t getRelativeRelocationType() const;
  
    std::string getDynamicTagAsString(unsigned Arch, uint64_t Type) const;
    std::string getDynamicTagAsString(uint64_t Type) const;
  
    /// Get the symbol for a given relocation.
    Expected<const Elf_Sym *> getRelocationSymbol(const Elf_Rel *Rel,
                                                  const Elf_Shdr *SymTab) const;
  
    static Expected<ELFFile> create(StringRef Object);
  
    bool isLE() const {
      return getHeader()->getDataEncoding() == ELF::ELFDATA2LSB;
    }
  
    bool isMipsELF64() const {
      return getHeader()->e_machine == ELF::EM_MIPS &&
             getHeader()->getFileClass() == ELF::ELFCLASS64;
    }
  
    bool isMips64EL() const { return isMipsELF64() && isLE(); }
  
    Expected<Elf_Shdr_Range> sections() const;
  
    Expected<Elf_Dyn_Range> dynamicEntries() const;
  
    Expected<const uint8_t *> toMappedAddr(uint64_t VAddr) const;
  
    Expected<Elf_Sym_Range> symbols(const Elf_Shdr *Sec) const {
      if (!Sec)
        return makeArrayRef<Elf_Sym>(nullptr, nullptr);
      return getSectionContentsAsArray<Elf_Sym>(Sec);
    }
  
    Expected<Elf_Rela_Range> relas(const Elf_Shdr *Sec) const {
      return getSectionContentsAsArray<Elf_Rela>(Sec);
    }
  
    Expected<Elf_Rel_Range> rels(const Elf_Shdr *Sec) const {
      return getSectionContentsAsArray<Elf_Rel>(Sec);
    }
  
    Expected<Elf_Relr_Range> relrs(const Elf_Shdr *Sec) const {
      return getSectionContentsAsArray<Elf_Relr>(Sec);
    }
  
    std::vector<Elf_Rel> decode_relrs(Elf_Relr_Range relrs) const;
  
    Expected<std::vector<Elf_Rela>> android_relas(const Elf_Shdr *Sec) const;
  
    /// Iterate over program header table.
    Expected<Elf_Phdr_Range> program_headers() const {
      if (getHeader()->e_phnum && getHeader()->e_phentsize != sizeof(Elf_Phdr))
        return createError("invalid e_phentsize: " +
                           Twine(getHeader()->e_phentsize));
  
      uint64_t HeadersSize =
          (uint64_t)getHeader()->e_phnum * getHeader()->e_phentsize;
      uint64_t PhOff = getHeader()->e_phoff;
      if (PhOff + HeadersSize < PhOff || PhOff + HeadersSize > getBufSize())
        return createError("program headers are longer than binary of size " +
                           Twine(getBufSize()) + ": e_phoff = 0x" +
                           Twine::utohexstr(getHeader()->e_phoff) +
                           ", e_phnum = " + Twine(getHeader()->e_phnum) +
                           ", e_phentsize = " + Twine(getHeader()->e_phentsize));
  
      auto *Begin = reinterpret_cast<const Elf_Phdr *>(base() + PhOff);
      return makeArrayRef(Begin, Begin + getHeader()->e_phnum);
    }
  
    /// Get an iterator over notes in a program header.
    ///
    /// The program header must be of type \c PT_NOTE.
    ///
    /// \param Phdr the program header to iterate over.
    /// \param Err [out] an error to support fallible iteration, which should
    ///  be checked after iteration ends.
    Elf_Note_Iterator notes_begin(const Elf_Phdr &Phdr, Error &Err) const {
      assert(Phdr.p_type == ELF::PT_NOTE && "Phdr is not of type PT_NOTE");
      ErrorAsOutParameter ErrAsOutParam(&Err);
      if (Phdr.p_offset + Phdr.p_filesz > getBufSize()) {
        Err = createError("PT_NOTE header has invalid offset (0x" +
                          Twine::utohexstr(Phdr.p_offset) + ") or size (0x" +
                          Twine::utohexstr(Phdr.p_filesz) + ")");
        return Elf_Note_Iterator(Err);
      }
      return Elf_Note_Iterator(base() + Phdr.p_offset, Phdr.p_filesz, Err);
    }
  
    /// Get an iterator over notes in a section.
    ///
    /// The section must be of type \c SHT_NOTE.
    ///
    /// \param Shdr the section to iterate over.
    /// \param Err [out] an error to support fallible iteration, which should
    ///  be checked after iteration ends.
    Elf_Note_Iterator notes_begin(const Elf_Shdr &Shdr, Error &Err) const {
      assert(Shdr.sh_type == ELF::SHT_NOTE && "Shdr is not of type SHT_NOTE");
      ErrorAsOutParameter ErrAsOutParam(&Err);
      if (Shdr.sh_offset + Shdr.sh_size > getBufSize()) {
        Err = createError("SHT_NOTE section " + getSecIndexForError(this, &Shdr) +
                          " has invalid offset (0x" +
                          Twine::utohexstr(Shdr.sh_offset) + ") or size (0x" +
                          Twine::utohexstr(Shdr.sh_size) + ")");
        return Elf_Note_Iterator(Err);
      }
      return Elf_Note_Iterator(base() + Shdr.sh_offset, Shdr.sh_size, Err);
    }
  
    /// Get the end iterator for notes.
    Elf_Note_Iterator notes_end() const {
      return Elf_Note_Iterator();
    }
  
    /// Get an iterator range over notes of a program header.
    ///
    /// The program header must be of type \c PT_NOTE.
    ///
    /// \param Phdr the program header to iterate over.
    /// \param Err [out] an error to support fallible iteration, which should
    ///  be checked after iteration ends.
    iterator_range<Elf_Note_Iterator> notes(const Elf_Phdr &Phdr,
                                            Error &Err) const {
      return make_range(notes_begin(Phdr, Err), notes_end());
    }
  
    /// Get an iterator range over notes of a section.
    ///
    /// The section must be of type \c SHT_NOTE.
    ///
    /// \param Shdr the section to iterate over.
    /// \param Err [out] an error to support fallible iteration, which should
    ///  be checked after iteration ends.
    iterator_range<Elf_Note_Iterator> notes(const Elf_Shdr &Shdr,
                                            Error &Err) const {
      return make_range(notes_begin(Shdr, Err), notes_end());
    }
  
    Expected<StringRef> getSectionStringTable(
        Elf_Shdr_Range Sections,
        WarningHandler WarnHandler = &defaultWarningHandler) const;
    Expected<uint32_t> getSectionIndex(const Elf_Sym *Sym, Elf_Sym_Range Syms,
                                       ArrayRef<Elf_Word> ShndxTable) const;
    Expected<const Elf_Shdr *> getSection(const Elf_Sym *Sym,
                                          const Elf_Shdr *SymTab,
                                          ArrayRef<Elf_Word> ShndxTable) const;
    Expected<const Elf_Shdr *> getSection(const Elf_Sym *Sym,
                                          Elf_Sym_Range Symtab,
                                          ArrayRef<Elf_Word> ShndxTable) const;
    Expected<const Elf_Shdr *> getSection(uint32_t Index) const;
  
    Expected<const Elf_Sym *> getSymbol(const Elf_Shdr *Sec,
                                        uint32_t Index) const;
  
    Expected<StringRef>
    getSectionName(const Elf_Shdr *Section,
                   WarningHandler WarnHandler = &defaultWarningHandler) const;
    Expected<StringRef> getSectionName(const Elf_Shdr *Section,
                                       StringRef DotShstrtab) const;
    template <typename T>
    Expected<ArrayRef<T>> getSectionContentsAsArray(const Elf_Shdr *Sec) const;
    Expected<ArrayRef<uint8_t>> getSectionContents(const Elf_Shdr *Sec) const;
    Expected<ArrayRef<uint8_t>> getSegmentContents(const Elf_Phdr *Phdr) const;
  };
  
  using ELF32LEFile = ELFFile<ELF32LE>;
  using ELF64LEFile = ELFFile<ELF64LE>;
  using ELF32BEFile = ELFFile<ELF32BE>;
  using ELF64BEFile = ELFFile<ELF64BE>;
  
  template <class ELFT>
  inline Expected<const typename ELFT::Shdr *>
  getSection(typename ELFT::ShdrRange Sections, uint32_t Index) {
    if (Index >= Sections.size())
      return createError("invalid section index: " + Twine(Index));
    return &Sections[Index];
  }
  
  template <class ELFT>
  inline Expected<uint32_t>
  getExtendedSymbolTableIndex(const typename ELFT::Sym *Sym,
                              const typename ELFT::Sym *FirstSym,
                              ArrayRef<typename ELFT::Word> ShndxTable) {
    assert(Sym->st_shndx == ELF::SHN_XINDEX);
    unsigned Index = Sym - FirstSym;
    if (Index >= ShndxTable.size())
      return createError(
          "extended symbol index (" + Twine(Index) +
          ") is past the end of the SHT_SYMTAB_SHNDX section of size " +
          Twine(ShndxTable.size()));
  
    // The size of the table was checked in getSHNDXTable.
    return ShndxTable[Index];
  }
  
  template <class ELFT>
  Expected<uint32_t>
  ELFFile<ELFT>::getSectionIndex(const Elf_Sym *Sym, Elf_Sym_Range Syms,
                                 ArrayRef<Elf_Word> ShndxTable) const {
    uint32_t Index = Sym->st_shndx;
    if (Index == ELF::SHN_XINDEX) {
      auto ErrorOrIndex = getExtendedSymbolTableIndex<ELFT>(
          Sym, Syms.begin(), ShndxTable);
      if (!ErrorOrIndex)
        return ErrorOrIndex.takeError();
      return *ErrorOrIndex;
    }
    if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
      return 0;
    return Index;
  }
  
  template <class ELFT>
  Expected<const typename ELFT::Shdr *>
  ELFFile<ELFT>::getSection(const Elf_Sym *Sym, const Elf_Shdr *SymTab,
                            ArrayRef<Elf_Word> ShndxTable) const {
    auto SymsOrErr = symbols(SymTab);
    if (!SymsOrErr)
      return SymsOrErr.takeError();
    return getSection(Sym, *SymsOrErr, ShndxTable);
  }
  
  template <class ELFT>
  Expected<const typename ELFT::Shdr *>
  ELFFile<ELFT>::getSection(const Elf_Sym *Sym, Elf_Sym_Range Symbols,
                            ArrayRef<Elf_Word> ShndxTable) const {
    auto IndexOrErr = getSectionIndex(Sym, Symbols, ShndxTable);
    if (!IndexOrErr)
      return IndexOrErr.takeError();
    uint32_t Index = *IndexOrErr;
    if (Index == 0)
      return nullptr;
    return getSection(Index);
  }
  
  template <class ELFT>
  Expected<const typename ELFT::Sym *>
  ELFFile<ELFT>::getSymbol(const Elf_Shdr *Sec, uint32_t Index) const {
    auto SymsOrErr = symbols(Sec);
    if (!SymsOrErr)
      return SymsOrErr.takeError();
  
    Elf_Sym_Range Symbols = *SymsOrErr;
    if (Index >= Symbols.size())
      return createError("unable to get symbol from section " +
                         getSecIndexForError(this, Sec) +
                         ": invalid symbol index (" + Twine(Index) + ")");
    return &Symbols[Index];
  }
  
  template <class ELFT>
  template <typename T>
  Expected<ArrayRef<T>>
  ELFFile<ELFT>::getSectionContentsAsArray(const Elf_Shdr *Sec) const {
    if (Sec->sh_entsize != sizeof(T) && sizeof(T) != 1)
      return createError("section " + getSecIndexForError(this, Sec) +
                         " has an invalid sh_entsize: " + Twine(Sec->sh_entsize));
  
    uintX_t Offset = Sec->sh_offset;
    uintX_t Size = Sec->sh_size;
  
    if (Size % sizeof(T))
      return createError("section " + getSecIndexForError(this, Sec) +
                         " has an invalid sh_size (" + Twine(Size) +
                         ") which is not a multiple of its sh_entsize (" +
                         Twine(Sec->sh_entsize) + ")");
    if (std::numeric_limits<uintX_t>::max() - Offset < Size)
      return createError("section " + getSecIndexForError(this, Sec) +
                         " has a sh_offset (0x" + Twine::utohexstr(Offset) +
                         ") + sh_size (0x" + Twine::utohexstr(Size) +
                         ") that cannot be represented");
    if (Offset + Size > Buf.size())
      return createError("section " + getSecIndexForError(this, Sec) +
                         " has a sh_offset (0x" + Twine::utohexstr(Offset) +
                         ") + sh_size (0x" + Twine::utohexstr(Size) +
                         ") that is greater than the file size (0x" +
                         Twine::utohexstr(Buf.size()) + ")");
  
    if (Offset % alignof(T))
      // TODO: this error is untested.
      return createError("unaligned data");
  
    const T *Start = reinterpret_cast<const T *>(base() + Offset);
    return makeArrayRef(Start, Size / sizeof(T));
  }
  
  template <class ELFT>
  Expected<ArrayRef<uint8_t>>
  ELFFile<ELFT>::getSegmentContents(const Elf_Phdr *Phdr) const {
    uintX_t Offset = Phdr->p_offset;
    uintX_t Size = Phdr->p_filesz;
  
    if (std::numeric_limits<uintX_t>::max() - Offset < Size)
      return createError("program header " + getPhdrIndexForError(this, Phdr) +
                         " has a p_offset (0x" + Twine::utohexstr(Offset) +
                         ") + p_filesz (0x" + Twine::utohexstr(Size) +
                         ") that cannot be represented");
    if (Offset + Size > Buf.size())
      return createError("program header  " + getPhdrIndexForError(this, Phdr) +
                         " has a p_offset (0x" + Twine::utohexstr(Offset) +
                         ") + p_filesz (0x" + Twine::utohexstr(Size) +
                         ") that is greater than the file size (0x" +
                         Twine::utohexstr(Buf.size()) + ")");
    return makeArrayRef(base() + Offset, Size);
  }
  
  template <class ELFT>
  Expected<ArrayRef<uint8_t>>
  ELFFile<ELFT>::getSectionContents(const Elf_Shdr *Sec) const {
    return getSectionContentsAsArray<uint8_t>(Sec);
  }
  
  template <class ELFT>
  StringRef ELFFile<ELFT>::getRelocationTypeName(uint32_t Type) const {
    return getELFRelocationTypeName(getHeader()->e_machine, Type);
  }
  
  template <class ELFT>
  void ELFFile<ELFT>::getRelocationTypeName(uint32_t Type,
                                            SmallVectorImpl<char> &Result) const {
    if (!isMipsELF64()) {
      StringRef Name = getRelocationTypeName(Type);
      Result.append(Name.begin(), Name.end());
    } else {
      // The Mips N64 ABI allows up to three operations to be specified per
      // relocation record. Unfortunately there's no easy way to test for the
      // presence of N64 ELFs as they have no special flag that identifies them
      // as being N64. We can safely assume at the moment that all Mips
      // ELFCLASS64 ELFs are N64. New Mips64 ABIs should provide enough
      // information to disambiguate between old vs new ABIs.
      uint8_t Type1 = (Type >> 0) & 0xFF;
      uint8_t Type2 = (Type >> 8) & 0xFF;
      uint8_t Type3 = (Type >> 16) & 0xFF;
  
      // Concat all three relocation type names.
      StringRef Name = getRelocationTypeName(Type1);
      Result.append(Name.begin(), Name.end());
  
      Name = getRelocationTypeName(Type2);
      Result.append(1, '/');
      Result.append(Name.begin(), Name.end());
  
      Name = getRelocationTypeName(Type3);
      Result.append(1, '/');
      Result.append(Name.begin(), Name.end());
    }
  }
  
  template <class ELFT>
  uint32_t ELFFile<ELFT>::getRelativeRelocationType() const {
    return getELFRelativeRelocationType(getHeader()->e_machine);
  }
  
  template <class ELFT>
  Expected<const typename ELFT::Sym *>
  ELFFile<ELFT>::getRelocationSymbol(const Elf_Rel *Rel,
                                     const Elf_Shdr *SymTab) const {
    uint32_t Index = Rel->getSymbol(isMips64EL());
    if (Index == 0)
      return nullptr;
    return getEntry<Elf_Sym>(SymTab, Index);
  }
  
  template <class ELFT>
  Expected<StringRef>
  ELFFile<ELFT>::getSectionStringTable(Elf_Shdr_Range Sections,
                                       WarningHandler WarnHandler) const {
    uint32_t Index = getHeader()->e_shstrndx;
    if (Index == ELF::SHN_XINDEX) {
      // If the section name string table section index is greater than
      // or equal to SHN_LORESERVE, then the actual index of the section name
      // string table section is contained in the sh_link field of the section
      // header at index 0.
      if (Sections.empty())
        return createError(
            "e_shstrndx == SHN_XINDEX, but the section header table is empty");
  
      Index = Sections[0].sh_link;
    }
  
    if (!Index) // no section string table.
      return "";
    if (Index >= Sections.size())
      return createError("section header string table index " + Twine(Index) +
                         " does not exist");
    return getStringTable(&Sections[Index], WarnHandler);
  }
  
  template <class ELFT> ELFFile<ELFT>::ELFFile(StringRef Object) : Buf(Object) {}
  
  template <class ELFT>
  Expected<ELFFile<ELFT>> ELFFile<ELFT>::create(StringRef Object) {
    if (sizeof(Elf_Ehdr) > Object.size())
      return createError("invalid buffer: the size (" + Twine(Object.size()) +
                         ") is smaller than an ELF header (" +
                         Twine(sizeof(Elf_Ehdr)) + ")");
    return ELFFile(Object);
  }
  
  template <class ELFT>
  Expected<typename ELFT::ShdrRange> ELFFile<ELFT>::sections() const {
    const uintX_t SectionTableOffset = getHeader()->e_shoff;
    if (SectionTableOffset == 0)
      return ArrayRef<Elf_Shdr>();
  
    if (getHeader()->e_shentsize != sizeof(Elf_Shdr))
      return createError("invalid e_shentsize in ELF header: " +
                         Twine(getHeader()->e_shentsize));
  
    const uint64_t FileSize = Buf.size();
    if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize ||
        SectionTableOffset + (uintX_t)sizeof(Elf_Shdr) < SectionTableOffset)
      return createError(
          "section header table goes past the end of the file: e_shoff = 0x" +
          Twine::utohexstr(SectionTableOffset));
  
    // Invalid address alignment of section headers
    if (SectionTableOffset & (alignof(Elf_Shdr) - 1))
      // TODO: this error is untested.
      return createError("invalid alignment of section headers");
  
    const Elf_Shdr *First =
        reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
  
    uintX_t NumSections = getHeader()->e_shnum;
    if (NumSections == 0)
      NumSections = First->sh_size;
  
    if (NumSections > UINT64_MAX / sizeof(Elf_Shdr))
      return createError("invalid number of sections specified in the NULL "
                         "section's sh_size field (" +
                         Twine(NumSections) + ")");
  
    const uint64_t SectionTableSize = NumSections * sizeof(Elf_Shdr);
    if (SectionTableOffset + SectionTableSize < SectionTableOffset)
      return createError(
          "invalid section header table offset (e_shoff = 0x" +
          Twine::utohexstr(SectionTableOffset) +
          ") or invalid number of sections specified in the first section "
          "header's sh_size field (0x" +
          Twine::utohexstr(NumSections) + ")");
  
    // Section table goes past end of file!
    if (SectionTableOffset + SectionTableSize > FileSize)
      return createError("section table goes past the end of file");
    return makeArrayRef(First, NumSections);
  }
  
  template <class ELFT>
  template <typename T>
  Expected<const T *> ELFFile<ELFT>::getEntry(uint32_t Section,
                                              uint32_t Entry) const {
    auto SecOrErr = getSection(Section);
    if (!SecOrErr)
      return SecOrErr.takeError();
    return getEntry<T>(*SecOrErr, Entry);
  }
  
  template <class ELFT>
  template <typename T>
  Expected<const T *> ELFFile<ELFT>::getEntry(const Elf_Shdr *Section,
                                              uint32_t Entry) const {
    if (sizeof(T) != Section->sh_entsize)
      return createError("section " + getSecIndexForError(this, Section) +
                         " has invalid sh_entsize: expected " + Twine(sizeof(T)) +
                         ", but got " + Twine(Section->sh_entsize));
    uint64_t Pos = Section->sh_offset + (uint64_t)Entry * sizeof(T);
    if (Pos + sizeof(T) > Buf.size())
      return createError("unable to access section " +
                         getSecIndexForError(this, Section) + " data at 0x" +
                         Twine::utohexstr(Pos) +
                         ": offset goes past the end of file");
    return reinterpret_cast<const T *>(base() + Pos);
  }
  
  template <class ELFT>
  Expected<const typename ELFT::Shdr *>
  ELFFile<ELFT>::getSection(uint32_t Index) const {
    auto TableOrErr = sections();
    if (!TableOrErr)
      return TableOrErr.takeError();
    return object::getSection<ELFT>(*TableOrErr, Index);
  }
  
  template <class ELFT>
  Expected<StringRef>
  ELFFile<ELFT>::getStringTable(const Elf_Shdr *Section,
                                WarningHandler WarnHandler) const {
    if (Section->sh_type != ELF::SHT_STRTAB)
      if (Error E = WarnHandler("invalid sh_type for string table section " +
                                getSecIndexForError(this, Section) +
                                ": expected SHT_STRTAB, but got " +
                                object::getELFSectionTypeName(
                                    getHeader()->e_machine, Section->sh_type)))
        return std::move(E);
  
    auto V = getSectionContentsAsArray<char>(Section);
    if (!V)
      return V.takeError();
    ArrayRef<char> Data = *V;
    if (Data.empty())
      return createError("SHT_STRTAB string table section " +
                         getSecIndexForError(this, Section) + " is empty");
    if (Data.back() != '\0')
      return createError("SHT_STRTAB string table section " +
                         getSecIndexForError(this, Section) +
                         " is non-null terminated");
    return StringRef(Data.begin(), Data.size());
  }
  
  template <class ELFT>
  Expected<ArrayRef<typename ELFT::Word>>
  ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section) const {
    auto SectionsOrErr = sections();
    if (!SectionsOrErr)
      return SectionsOrErr.takeError();
    return getSHNDXTable(Section, *SectionsOrErr);
  }
  
  template <class ELFT>
  Expected<ArrayRef<typename ELFT::Word>>
  ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section,
                               Elf_Shdr_Range Sections) const {
    assert(Section.sh_type == ELF::SHT_SYMTAB_SHNDX);
    auto VOrErr = getSectionContentsAsArray<Elf_Word>(&Section);
    if (!VOrErr)
      return VOrErr.takeError();
    ArrayRef<Elf_Word> V = *VOrErr;
    auto SymTableOrErr = object::getSection<ELFT>(Sections, Section.sh_link);
    if (!SymTableOrErr)
      return SymTableOrErr.takeError();
    const Elf_Shdr &SymTable = **SymTableOrErr;
    if (SymTable.sh_type != ELF::SHT_SYMTAB &&
        SymTable.sh_type != ELF::SHT_DYNSYM)
      return createError("SHT_SYMTAB_SHNDX section is linked with " +
                         object::getELFSectionTypeName(getHeader()->e_machine,
                                                       SymTable.sh_type) +
                         " section (expected SHT_SYMTAB/SHT_DYNSYM)");
  
    uint64_t Syms = SymTable.sh_size / sizeof(Elf_Sym);
    if (V.size() != Syms)
      return createError("SHT_SYMTAB_SHNDX has " + Twine(V.size()) +
                         " entries, but the symbol table associated has " +
                         Twine(Syms));
  
    return V;
  }
  
  template <class ELFT>
  Expected<StringRef>
  ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec) const {
    auto SectionsOrErr = sections();
    if (!SectionsOrErr)
      return SectionsOrErr.takeError();
    return getStringTableForSymtab(Sec, *SectionsOrErr);
  }
  
  template <class ELFT>
  Expected<StringRef>
  ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec,
                                         Elf_Shdr_Range Sections) const {
  
    if (Sec.sh_type != ELF::SHT_SYMTAB && Sec.sh_type != ELF::SHT_DYNSYM)
      return createError(
          "invalid sh_type for symbol table, expected SHT_SYMTAB or SHT_DYNSYM");
    auto SectionOrErr = object::getSection<ELFT>(Sections, Sec.sh_link);
    if (!SectionOrErr)
      return SectionOrErr.takeError();
    return getStringTable(*SectionOrErr);
  }
  
  template <class ELFT>
  Expected<StringRef>
  ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section,
                                WarningHandler WarnHandler) const {
    auto SectionsOrErr = sections();
    if (!SectionsOrErr)
      return SectionsOrErr.takeError();
    auto Table = getSectionStringTable(*SectionsOrErr, WarnHandler);
    if (!Table)
      return Table.takeError();
    return getSectionName(Section, *Table);
  }
  
  template <class ELFT>
  Expected<StringRef> ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section,
                                                    StringRef DotShstrtab) const {
    uint32_t Offset = Section->sh_name;
    if (Offset == 0)
      return StringRef();
    if (Offset >= DotShstrtab.size())
      return createError("a section " + getSecIndexForError(this, Section) +
                         " has an invalid sh_name (0x" +
                         Twine::utohexstr(Offset) +
                         ") offset which goes past the end of the "
                         "section name string table");
    return StringRef(DotShstrtab.data() + Offset);
  }
  
  /// This function returns the hash value for a symbol in the .dynsym section
  /// Name of the API remains consistent as specified in the libelf
  /// REF : http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash
  inline unsigned hashSysV(StringRef SymbolName) {
    unsigned h = 0, g;
    for (char C : SymbolName) {
      h = (h << 4) + C;
      g = h & 0xf0000000L;
      if (g != 0)
        h ^= g >> 24;
      h &= ~g;
    }
    return h;
  }
  
  } // end namespace object
  } // end namespace llvm
  
  #endif // LLVM_OBJECT_ELF_H
  